In the fabrication and installation of metal pipe and fittings of comparatively large diameter, the shear size and weight of the pipe lengths and the various transitional connections make it impractical to provide threaded ends which can be joined and sealed by rotation, as is common with relatively small diameter iron or steel pipes and fittings. It is therefore customary to position such pipe lengths and fittings successively in mating alignment and then apply annular weld beads to unitize the installation. In smaller pipe sizes it is often necessary to utilize a welding procedure to join the pipe components either because the material composition of the components is resistant to the provision of threaded ends which may be joined by rotation or because welding jointure requirements are dictated by the intended special use and are mandatory in the specifications for the installation.
The time required for preparing each jointure by pipe fitters in order to complete a predetermined layout is often tedious and cumbersome, particularly when the work is being performed insitu. The use of holding fixtures, as are normally available in a workshop environment, is not practical, and the careful positioning and temporary retention of each successive workpiece and the application of successive weld beads is a laborious process. It is common for at least two workmen to be involved in such pipe fitting practice. The steps they must perform for each jointure include positioning the workpieces by visual approximation, tack welding the workpieces along the intended line of jointure whereby some limited angular movement between the workpieces can still be effected, completing final accurate alignment of the work pieces relative to each other through the use of several large carpenter squares, and then applying an annular weld bead along the jointure line to firmly unitize and seal the joint. This procedure is repeated successively with the addition of each pipe length and fitting, and is particularly cumbersome because of the difficulties associated with manipulation of the squaring tools to properly position the workpieces.
The aforementioned fitting and welding procedure may be simplified and expedited through the provision and use of a specially designed locating and positioning instrument to replace the several carpenter's squares normally employed. A device for this purpose which has some obvious advantages to the pipe fitter has been previously disclosed in Canadian Pat. No. 697,863. There remains, however, a need for an improved, more versatile pipe fitter's instrument to expedite the weld jointure of diverse special purpose fittings in the arrangements which confront pipe fitters.